Effect of 5-hydroxydopamine on the large dense-cored vesicles in the axon terminals of the myenteric ganglia of the guinea-pig stomach.

Quantitative ultrastructural analysis revealed that the large dense-cored vesicles in the axon terminals in the myenteric ganglia of the guinea-pig stomach tend to be concentrated towards the ends of the terminals. In guinea-pigs treated with 50 mg/kg 5-hydroxydopamine, diameters of the vesicles were increased and their distribution in the terminals was altered. Treatment with reserpine prior to 5-hydroxydopamine increased the proportion of large dense-cored vesicles and decreased the overall number of vesicles in the terminals. The diameter of the vesicles was increased both in the terminal profiles and in the non-terminal segments of the axons. These observations are consistent with the view that uptake of 5-hydroxydopamine into small vesicles is followed by their transformation into large dense-cored vesicles.

Distribution and diameter of large dense-cored vesicles in axon terminals in the myenteric ganglia of the mouse and hamster stomach.

The distribution and diameter of the large dense-cored vesicles in axon terminals in the myenteric ganglia of the mouse and hamster stomach were analyzed in electron micrographs of groups of 150 terminal profiles. In the mouse, the vesicles were proportionately more numerous and larger than in the hamster; they were also larger in terminal profiles containing more than 20% of the vesicles. There was no evidence of bimodality of the distribution curve of the proportion of large dense-cored vesicles/profile in either animal. The presence of a significant degree of skew of the distribution curves was indicative of uneven distribution of the vesicles in the terminals, and the occurrence of a significant inverse correlation between the proportion of large dense-cored vesicles/profile and both the diameter of the profiles and the total number of vesicles/profile was in agreement with subjective evidence of a tendency towards accumulation of the vesicles at the ends of the terminals.

Location in the nodose ganglion of the perikarya of neurons whose axons distribute in the epithelium of the rat trachea.

The numbers of axons/unit length and of axons/group in the epithelium of the right and left sides of the trachea were determined in longitudinally orientated sections of specimens taken from five control rats, and from groups of five or six rats three days after section of the left vagus nerve above or below the nodose ganglion or section of the superior laryngeal and pharyngeal branches of the left vagus. After section of the vagus nerve below the nodose ganglion, there was a highly significant reduction in the number of axons/unit length in the epithelium of the ipsilateral side of the trachea, a significant reduction in the number of axons/group on this side and a small reduction in the number of axons/unit length on the contralateral side. The absence of similar changes in specimens from rats in which the vagus nerve was sectioned above the nodose ganglion, and in rats in which the branches from the ganglion were sectioned, indicated that the intraepithelial axons are derived from neurons whose perikarya are located in the ganglion and is consistent with the view that the axons are afferent. In addition to axons with terminals which resembled those which, in other tissues, have been defined as pain afferents, occasional axons with terminals containing numerous small clear vesicles were identified in the epithelium. The absence of these axons from the epithelium only in specimens taken from the ipsilateral side of the trachea after infranodose section of the left vagus nerve suggests that these may also be afferent.

Effect of capsaicin on the intraperitoneal axons of the rat trachea.

In vitro exposure of specimens of rat trachea to capsaicin at a concentration of 2 x 10(-4) g/ml was followed by a significant increase in the diameter and major changes in the vesicle content of intraepithelial axons with terminals containing a high proportion of large dense-cored vesicles and only scattered small vesicles, but had no effect on axons with terminals containing large numbers of closely-packed small vesicles. Twenty-four hours after in vivo treatment of rats with capsaicin at dose levels of 50 mg/kg, there was a highly significant reduction in the number of axons/unit length in the tracheal epithelium. This was attributed to similar patterns of degeneration of axons with terminals containing a high proportion of large dense-cored vesicles to those seen in the ureter and to the early elimination of the degenerating axons by phagocytosis by the epithelial cells.

Substance P-like immunoreactivity in the intramural nerve plexuses of the guinea-pig ureter: a light and electron microscopical study.

Immunofluorescence and immunoperoxidase techniques were used to study the distribution of substance P-like immunoreactivity in the intramural nerve plexuses of the guinea-pig ureter. In light microscopical preparations, immunoreactivity was observed in plexuses related to the muscle coat as well as in plexuses in the submucosa and beneath the epithelium. Ultrastructural examination showed that the immunoreactivity was located primarily in axons in the nerves. In perfusion-fixed specimens, there was evidence of its presence both in axons with terminals containing mainly large dense-cored vesicles and in axons with terminals containing mainly small vesicles. The presence of substance P-like immunoreactivity in axons with terminals containing mainly large dense-cored vesicles was supported by examination of specimens treated in vitro with capsaicin. In these specimens, the axons were dilated and showed a number of other changes in fine structure. There was also a substantial reduction in the amount of immunoreactivity in the nerve plexuses and the dilated axons contained little if any reaction product. The possibility that axons which contained large amounts of reaction product after treatment with capsaicin represented axons with terminals containing mainly small vesicles was discussed. Comparison of the distribution of the different types of small vesicle-containing terminal identified in glutaraldehyde-fixed material with that of axons containing reaction product suggested that the immunoreactivity present in such axons was located in those in which the small vesicles in the terminals were clear rather than those in which the vesicles contained dense material.